Conventional fluorescent fixtures utilize ballasts which are positioned within a ballast case comprised of a flat base portion and a cover portion secured thereto. The conventional ballasts normally include a core and coil subassembly mounted on one end of the base portion with the terminations of the coils extending therefrom. The core and coil assembly is preferably positioned in the case so that the assembly is spaced from the top surface of the case and the sides thereof, for heat and sound insulation purposes. During the manufacture of the ballast, elongated flexible external leads are electrically connected to predetermined coil terminations. The total subassembly may then be encased in an asphalt silica sand potting compound. The ballast cover is then secured over the ballast components with the flexible leads extending outwardly from the case. These discrete external leads are subsequently electrically connected to leads or terminals in lamp holders or the like.
While the above described fixtures are generally satisfactory in operation, they do suffer several drawbacks or disadvantages. One disadvantage of prior art fixtures is that different lamp manufacturers require ballasts having leads of different lengths, thereby requiring the ballast manufacturer to produce, and inventory, ballasts having various lead lengths. Further, each individual manufacturer may require various length leads to accommodate various lamp fixtures.
One form of a ballast which overcomes several of the problems associated with ballasts having discrete leads, is the "leadless ballast" disclosed in U.S. patent application Ser. No. 257,528, filed Oct. 14, 1988 entitled "An Improved Ballast", the disclosure of which is incorporated herein by reference. The ballast of the co-pending application may be described as a "leadless ballast" in view of the fact that no discrete external leads extend from the ballast. Rather, the core and coil subassembly is mounted in one end of the case, and has terminal pins extending from one end of the core and coil subassembly which are connected to an electrical connector means. The ballast case is provided with an access opening formed in the top thereof to facilitate the extension or insertion of one end of a wiring harness therethrough, which is then fitted to form a "pressure lock" connection with the electrical connector means and to complete the desired wiring circuit.
While the invention disclosed and described in the co-pending application is an improvement over ballasts having discrete leads, there are several instances where it still has drawbacks or disadvantages. One drawback is in the use of the above-described ballast in a totally unitized lamp holder, lamp socket, ballast connector harness assembly which is mounted integral with the light fixture, as described in the co-pending patent application entitled "Fluorescent Fixture Housing with Integral Lamp Sockets and Electrical Connections", filed simultaneously herewith, the disclosure of which is incorporated herein by reference. An electrical connection on the top portion of the ballast would not allow the ballast to be quickly and easily connected to a wiring harness mounted on the base of the fixture housing.
One additional drawback of the ballast of the co-pending application, Ser. No. 257,538, is in the use of a pressure lock connection between the wiring harness and the connector means. A release comb is necessary to maintain the electrical connections between the wiring harness and the connector pins. The use of a release comb is one additional component which must be manufactured and installed, adding time and labor costs.
Another drawback to prior art ballasts is in the large number of interconnections from the coils of the ballast to the eventual lamp holder contacts. A large number of interconnections reduces the reliability of the ballast and the total system. A large number of interconnections also increases the cost of the ballast because of the more complex configuration.
It is therefore a general object of the present invention to provide an improved leadless ballast.
Yet another object of the present invention is to provide a leadless ballast which lends itself to mechanized manufacture, thereby reducing the cost of the ballast.
Still another object of the present invention is to provide a ballast which is mechanizable for fixture assembly to reduce fixture assembly labor costs.
Still another object of the invention is to provide a leadless ballast which permits an inventory reduction of ballasts.
A further object of the invention is to provide a ballast having an end connector to facilitate electrical connection thereof to a wiring harness extending from a lamp fixture.
Still a further object of the invention is to provide a ballast which is adapted for use in a fluorescent lamp fixture having integral lamp holders and electrical connections.
These and other objects of the present invention will be apparent to those skilled in the art.